1. Field of the Invention
This invention relates generally to waterbed mattress, and more particularly to a perimeter support for a waterbed mattress.
2. Description of the Prior Art
Waterbeds have become a popular alternative to conventional type bedding because of their superior relaxation inducing properties. Generally a waterbed has a flexible bladder filled with liquid such as water. The body supported by the mattress displaces fluid in the bladder until an equilibrium condition is established to provide uniform pressure support of the body. However, since the flexible bladder has soft sides, the mattress must be laterally supported about its perimeter to maintain the mattress at a pre-selected uniform height to permit a body to be effectively supported by the mattress without "bottoming out". When the mattress "bottoms out", the pressure distribution supporting the body is no longer uniform and the beneficial aspects of the waterbed are negated. One type of perimeter support is a solid frame about the periphery of the bladder. However, solid frames are uncomfortable to one sitting on the bedside or getting in or out of the bed, and do not readily accept conventional bed clothes.
To overcome these problems, a perimeter chamber filled with air or foam material has typically been provided as shown in U.S. Pat. Nos. 3,840,921 and 4,006,501. As shown in these patents the air or foam material in the perimeter chamber accomplishes the desired results of providing sufficient lateral support to maintain the mattress at a pre-selected uniform height while being comfortable to one sitting on the bedside or getting in and out of the bed. However, in the known perimter chamber waterbed mattresses, the chamber has been formed integrally with the liquid-containing bladder of the mattress. Thus, when the perimeter chamber is damaged such as by an external puncturing of the chamber, the entire mattress must be replaced. Further when there is an internal failure of the chamber seams due to action of, or reaction with, the liquid, the liquid enters the chamber and destroys its effectiveness as a perimeter support (again requiring the entire mattress to be replaced).